Today, mobile e-commerce websites aren’t working: Ten-step shopping carts, mandatory account signup, slow page loads. When we get linked to a shopping cart on our phone, we usually just give up. That shouldn’t be surprising—most mobile shopping sites are fundamentally the same as the desktop sites that preceded them, despite the medium calling for something completely different.

The result has been predictable. Despite mobile devices representing 60% of browsing traffic for shopping sites, they only make up 15% of purchases.

What does work? Native mobile apps, like Postmates or Instacart, with buying experiences designed to let the user transact as quickly as possible, reuse existing payment details across many orders, and finish the entire transaction in the same app they started in.

Over the past year, a number of companies—Twitter, Pinterest, and Spring, to name a few—have worked to bring this kind of experience to e-commerce, pulling products from many stores into the very apps where users are already spending their time.

While this works, experiences like this are hard to build, since stores don’t usually make their products programmatically available.

So, we’re trying out something new. We’re launching Relay, an API for stores to publish their products, and for apps to read them. Relay makes it easier for developers to build great mobile e-commerce experiences, and for stores to participate in them.

It’s powered by a few new objects in the Stripe API: Products, SKUs (product variants), and Orders. Stores can provide product information to Stripe via the dashboard, the API, or by linking their existing e-commerce systems. SAP Hybris (used by stores like Levi’s, Oakley, and Ted Baker) is the first e-commerce integration we’re announcing, but expect more to come later.

For stores, you can use Relay to enable instant purchases in third-party mobile apps: one of our launch partners, Twitter, is using Relay to enable anyone to start selling within tweets. (You can try it out on this Tweet from @WarbyParker.) Or you can submit your products to be shown in a growing number of apps like ShopStyle and Spring.

For app developers, Relay is a set of APIs for building great in-app buying experiences. People can buy products directly within your app rather than getting pushed to third-party websites. Our friends at Wish have made their product catalog accessible starting today via Relay. You can play around with their data and see what kinds of buying experiences you could build.